A font's height in typography is utilized differently in some CAD programs.   Generally, in page layout programs (and Vectorworks I believe), the size of a font is based upon the "Em square".  An Em square is essentially a box for a character to sit within and is equal to the font's height, not a specific character's height.  This provides a space for characters such as a capital M and a lowercase g to fit within a given space and line up correctly.  It's all based on old school metal